1. Field of the Invention
The present invention is in the field of systems for automatically changing the crankcase oil of an internal combustion engine while the engine is operating, and for providing fresh makeup oil when a low crankcase oil level is sensed.
2. Description of the Prior Art
Systems have been known and used in the art for a number of years for automatically changing internal combustion engine crankcase oil during engine operation, with used crankcase oil being removed in small increments on a periodic basis controlled by a timer or other means, and with fresh makeup oil being supplied to replace the periodically removed used crankcase oil and also crankcase oil consumed by engine operation in response to the sensing of a low crankcase oil level by a sensor located in the crankcase. For diesel engines, it has been common to conduct the periodically removed used crankcase oil to the fuel tank, where the used oil became commingled with the fuel and was burned off with the fuel during engine operation. The first such system of which applicant is aware was developed and marketed by Power Plus Corporation of San Marcos, Calif., a corporation of which applicant is currently chairman of the board of directors. This prior system of Power Plus Corporation was marketed in the 1970s, and employed a timer for periodically actuating a reciprocating metering device to extract a small increment of used oil from the crankcase of a diesel engine and direct the increment to the fuel tank for burnoff with the fuel. In this system, fresh makeup oil was incrementally pumped from a fresh oil tank by a similar reciprocating metering device which was actuated in response to low-level sensing of the crankcase oil level. The low-level sensing makeup replaced both the used oil which was periodically extracted and burned off with the fuel and crankcase oil consumed by engine operation. Thus, both automatic oil changing and automatic oil makeup were provided during engine operation by this prior Power Plus Corporation system.
Applicant is aware of three prior art patents which disclose generally similar systems for automatically changing diesel engine crankcase oil and burning off the used oil with the fuel, and for providing makeup oil by means of low crankcase oil level sensing. One of these is the Yasuhara U.S. Pat. No. 4,417,561 wherein used crankcase oil is periodically valved by an odometer switch to the fuel tank, and fresh oil is gravity fed from a fresh oil tank to the crankcase by a valve controlled by a crankcase oil level switch. The quantity of each increment of burnoff oil removed from the crankcase is controlled by a timer. The Hurner U.S. Pat. No. 4,421,078 discloses a similar system for changing and making up crankcase oil during engine operation, in which a one-way cylinder is reloaded with an increment of used crankcase oil by pressure of the oil, and is periodically emptied by air pressure operation to the fuel tank. Fresh makeup oil is driven from an oil reservoir to the crankcase, also by air pressure, in response to low level dipstick sensing. A similar system is also disclosed in the Hurner U.S. Pat. No. 4,495,909. Applicant is aware of only one prior art patent, the Bonfilio U.S. Pat. No. 3,447,636, which discloses a system for changing engine oil while the engine is operating that employs a fresh oil-containing hydraulic cylinder actuated to eject the fresh oil by used, pressurized crankcase oil which is removed from the crankcase. In the Bonfilio system, the cylinder contains a supply of fresh oil sufficient for a complete engine oil change, and the entire supply of used crankcase oil except what may be in the oil filter and a small bleeder line actuates the cylinder and replaces the fresh oil that was in the cylinder in response to the manual closing of an electrical switch, for a one-shot complete oil change. Most of the fresh oil from the cylinder is stored in a temporary storage tank while most of the used engine oil displaces it in the cylinder for the express purpose of avoiding any substantial intermingling of spent oil and fresh oil, so that substantially all oil is removed from the crankcase during the oil changing event while the engine is running. Those skilled in the art will understand that the resulting substantially complete lack of oil in the crankcase will be likely to result in serious engine damage.
Applicant is aware of a number of other patents which dispose fresh oil makeup systems without oil changing. Thus, the Scott U.S. Pat. No. 4,299,307 discloses manual valving of makeup oil to the crankcase when low level is sensed either by a pressure sensor or by a float switch: the Zeidler et al. U.S. Pat. No. 4,105,092 discloses a dual pump system in which a relatively greater capacity pump holds crankcase oil level at its input; the Lang U.S. Pat. Nos. 4,091,894 and 4,091,895 disclose barometric type crankcase oil makeup systems wherein fresh oil is enabled to flow in the crankcase when an air-carrying sensor tube becomes uncovered as the oil level drops; the Gulla U.S. Pat. No. 3,882,967 discloses crankcase makeup in response to temperature-sensitive resistors in the crankcase arranged to be sequentially uncovered; the Rath, Jr. U.S. Pat. No. 3,876,037 discloses crankcase oil makeup pursuant to thermistor sensing, but which does not appear to be automatic; and the Norton U.S. Pat. No. 2,836,259 discloses crankcase oil makeup by a centrifugal pump responsive to a crankcase oil level sensor which may be a float, oil pressure device or diaphragm.
Merritt U.S. Pat. No. 4,674,456 discloses a system for effecting periodic partial replacement of used oil with fresh oil. A first container holds fresh oil, a second container holds used oil, and separate pumps transfer fresh oil to the engine and remove used oil. Oil level detectors can be provided in either container. In operation, fresh oil approximating the total capacity of the crankcase or oil reservoir is poured into the first container. In the example provided by the patentee, if the manufacturer recommends that five quarts of oil be replaced every 3000 miles, the patented system is programmed to remove one quart of used oil after 600 miles. Fresh oil is added "at a substantially equal rate to maintain a constant amount of oil within the oil reservoir of the engine". If one quart is removed, adding fresh oil at a substantially equal rate may result in a low oil level in the oil reservoir. There does not appear to be any means for compensating for oil burned in the engine, nor does there appear to be any means for sensing the oil level in the oil reservoir. In contrast, applicant's method and apparatus sense the oil level at all times, and add and remove small, substantially equal increments of oil in a manner coordinated with crankcase oil level sensing probes.
A plurality of probes are preferably located in fluid communication with the crankcase sump at spaced apart locations. The oil levels in such locations are typically at different levels, according to the orientation of the engine, such as when the engine is tipped going up or down hills or when going around corners. In such instances the separate sensor signals from the probes are indicative of the individual oil levels, and these signals are utilized to develop an average signal representative of the oil level in the crankcase sump for level engine orientation.
Applicant is not aware of any prior art system for automatically changing crankcase oil and making up crankcase oil level while an engine is running which periodically displaces an increment of used oil from the engine lubricating oil system and simultaneously replaces the used oil with an equal increment of new oil so that crankcase oil level does not lower during the incremental oil changing events.
Applicant is also not aware of any prior art system for changing and making up crankcase oil during engine operation in which the used oil extracted from the engine lubricating oil system is selectively routed either to the fuel tank or a holding tank in an oil change mode of operation, or back to the crankcase in an oil makeup mode of operation, in response to automatic crankcase oil level sensing. Applicant further is not aware of any prior art system for changing and making up engine lubricating oil during engine operation in which hydraulic cylinder means produces displacement of both used engine lubricating oil and fresh engine lubricating oil for both the oil change mode of operation and the makeup mode of operation. Applicant is also not aware of the use of multiple probes located in fluid communication with the crankcase sump to provide signals which can be processed to provide an average signal representative of the oil level in the crankcase for normal engine orientation.